1. Field of the Invention
The present invention relates to a wiper system, which wipers a windshield of a vehicle, and also relates to a method for controlling such a wiper system.
2. Description of Related Art
In general, a wiping speed of wipers of a vehicle wiper system can be changed. For example, in the wiper system, an operational mode of the wipers may be switched to one of a low speed wiping mode (hereinafter, referred to as “LOW mode”), a high speed wiping mode (hereinafter, referred to as “HIGH mode”) and an intermittent wiping mode (hereinafter, referred to as “INT mode”). The LOW mode is for wiping at a constant low speed. The HIGH mode is for wiping at a constant high speed. The INT mode is for intermittently executing the wiping movement at the constant low speed. Furthermore, in the INT mode, an intermittent stop time interval can be changed. The switching of the wiping speed is performed by controlling the rotational speed of a wiper motor thorough a pulse width modulation (PWM) control operation.
For example, Japanese Unexamined Patent Publication No. H05-319213 discloses a washer mode, in which reciprocal wiping movement of wipers is automatically repeated several times right after spraying of washer fluid over the windshield to remove dirt, which adheres to the windshield. In this washer mode, normal dirt can be removed within a short period of time with a small quantity of washer fluid. However, it is difficult to remove heavy dirt (e.g., a bird dropping, a smashed bug) within the short period of time with the small quantity of washer fluid. Thus, in order to remove the heavy dirt, the washer fluid needs to be sprayed several times or more, and the wipers need to be reciprocally moved accordingly. As a result, the required time and the required quantity of washer fluid are disadvantageously increased.